An optical pick-up that writes or reads an information signal on the optical recording medium such as the optical disc has been hitherto employed. The optical pick-up of this type has a light source such as a semiconductor laser to irradiate the optical recording medium with an optical beam emitted from the light source through an objective lens. Then, the information signal is written in the optical recording medium by the optical beam with which the optical recording medium is irradiated, or the reflected light of the optical beam applied to the optical recording medium is detected to read the information signal. One example of this kind of optical pick-up is disclosed in Japanese Patent Application Laid-open No. 2001-110068.
In recent years, to increase the storage capacity of the optical recording medium on which the information signal is recorded, a multi-layer optical disc has been proposed in which information recording layers for storing information are laminated in multi-layers in the direction of the thickness of the recording medium. When the information signal is recorded or reproduced on the multi-layer optical disc by the above-described optical pick-up, the condensing point of the optical beam by the objective lens can be made to exist on each information recording layer.
In such multi-layer optical discs, reflecting characteristics are different depending on the number of the information recording layers. Accordingly, when the information signal recorded on the information recording layer is recorded or reproduced by using the optical pick-up, various kinds of settings are required, for instance, an optical output is changed depending on what number of layers the information recording layer is piled. Specifically, a two-layer disc needs a recording and reproducing power about two times as high as that of one-layer disc. Likewise, three and four-layer discs need the recording and reproducing power not lower than the above-described power. Further, a case may be arise in which an amount of spherical aberration on a signal recording surface needs to have a satisfactory value by changing an amount of spherical aberration of light outputted from the optical pick-up in accordance with the thickness of a cover layer changing depending on the number of layers of the information recording layers.
Further, in a compatible optical disc apparatus in which already practically used DVD (Digital Versatile Disc) and CD (Compact Disc) can be selectively employed, when the kind of the optical disc to be mounted on the apparatus is discriminated, a complicated discriminating work is necessary. What is called a Blue Ray Disc (BD) as the optical disc that uses, in future, a blue color laser having wavelength shorter than that of the usually employed optical beam for recording and reproducing operations needs to discriminate discs more rapidly, as corresponding formats more increase.
When the information signal is recorded on the optical recording medium or the information signal recorded on the optical recording medium is reproduced by the optical disc apparatus having the optical pick-up as described above, if it is discriminated which of the optical discs including a BD, a DVD, a CD, etc. the optical recording medium is on which the information signal is tried to be recorded or reproduced at the present time, and whether the optical recording medium has a single information recording layer or a plurality of information recording layers, the reading operation of a discriminating signal recorded on the optical recording medium needs to be repeated. Further, the setting of the optical pick-up needs to be changed in accordance with whether or not the signal can be read, which of kinds of formats, for instance, ROM, ±R, ±RW, RAM, RE, etc. the kind of a format of the optical recording medium is, or what number of information recording layers are laminated from the read discriminating signal. Consequently, a great time loss is supposed to arise until a recording or a reproducing process is started.
When such a discriminating signal is read, there sometimes occurs a case that the wavelength or the intensity of light of the optical beam emitted from the light source of the optical pick-up cannot be set to a wavelength and an intensity of light necessary for performing an optimum recording and reproducing process, so that they need to be reset many times. Thus, when the recording and reproducing process is started, an operation is undesirably unstable.